Outcome of Staphylococcus aureus Bacteremia in Patients with Eradicable Foci versus Noneradicable Foci
CID
Outcome of Staphylococcus aureus Bacteremia in Patients with Eradicable Foci versus Noneradicable Foci
Sung-Han Kim 2 3
Wan-Bum Park 2 3
Ki-Deok Lee 2 3
Cheol-In Kang 2 3
Hong-Bin Kim 2 3
Myoung-don Oh 0 2 3
Eui-Chong Kim 0 1 3
Kang-Won Choe 0 2 3
0 Clinical Research Institute, Seoul National University Hospital , Seoul , Republic of Korea
1 Laboratory Medicine, Seoul National University College of Medicine
2 Internal Medicine
3 Departments of
To determine the outcome of Staphylococcus aureus bacteremia (SAB) on mortality, including the impact of methicillin resistance and an initial delay ( 48 h) of appropriate antibiotics, a retrospective cohort study including 238 patients with SAB was performed. By logistic regression, noneradicable or noneradicated foci, underlying cirrhosis, and cancer were found to be independent predictors of mortality. In patients with eradicable foci, there were no significant differences in the associated mortality rate between methicillinresistant SAB (11%) and methicillin-susceptible SAB (13%), and between inappropriate (13%) and appropriate (10%) empirical therapy, respectively (P p .79 and P p .78, respectively). By logistic regression, it was found that, in the subgroup of patients with noneradicable foci, underlying cirrhosis (odds ratio [OR], 3.1) and methicillin-resistant SAB (OR, 2.4) were independently associated with mortality.
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Staphylococcus aureus is a major cause of hospital- and
community-acquired infections, including bacteremia,
endocarditis, pneumonia, septic arthritis, and wound
infection. Despite several potent antistaphylococcal
drugs, S. aureus bacteremia (SAB) is still a serious
infection [
1
]. In recent years, some investigators have
emphasized the importance of focus identification and
eradication in the treatment of SAB [
2, 3
]. Furthermore,
although the rate of the resistance to methicillin among
S. aureus is increasing, the clinical impact of methicillin
resistance remains controversial [4]. Besides this,
because of the recent emergence of S. aureus resistant to
vancomycin [
5
], the prudent use of vancomycin is
essential. However, with some cases, methicillin-resistant
S. aureus (MRSA) infections are not initially suspected
because clues for S. aureus infection are lacking, and
microbiological results, including antibiotic
susceptibility data, are usually unavailable for 2 days.
However, the relative effects of a delay in appropriate
antibiotic treatment on the outcomes of patients with SAB
are also unclear [
4
].
In this study, we evaluated the risk factors
influencing the outcome of SAB. Furthermore, we
compared the outcomes of SAB in patients with eradicable
focus versus noneradicable focus and determined the
impact of methicillin resistance on the outcome for
patients with SAB and the effect of the inappropriate
empirical antibiotic treatment on the outcome for
patients with SAB.
PATIENTS, MATERIALS, AND METHODS
Study population. Seoul National University
Hospital is a university-affiliated tertiary care hospital with
1500 beds. The hospital provides specialized medical
and surgical care, including bone marrow
transplantation for adult (115 years of age) patients.
All patients with blood cultures positive for S. aureus
were identified from a retrospective review of the computerized
records of the Clinical Microbiology Laboratory for the period
of 1 January 1998 through 31 October 2001. Only the first
episode of SAB for each patient was included in the analysis. SAB
without clinical significance and SAB with a mixture of organisms
being cultivated from their blood samples were excluded.
Microbiological tests. Identification of S. aureus was
performed with Vitek GPI Cards. Antibiotic susceptibilities were
determined using the disk diffusion method, following the
recommendations of the NCCLS [
6
].
Definitions. Bacteremia was defined as the presence of 1
positive blood culture for S. aureus. It was considered clinically
significant if S. aureus was isolated from 1 blood culture and
if the patients had signs and symptoms consistent with
bacteremia [
7
]. No cases in which S. aureus was cultivated only
in a peripheral intravenous line were included. SAB was
considered to have been community acquired if S. aureus was
isolated from cultures of blood samples obtained within 48 h
after hospital admission, if the patient had not transferred from
another hospital, and if the patient had any symptoms or signs
suggestive of infection at admission [
2
]. Otherwise, SAB was
considered to have been hospital acquired.
Previous antibiotic use was defined as treatment with
antibiotics for 17 days during the month before the onset of SAB
[
7
]. Previous surgery was defined as an operation within the
month before the onset of SAB [
7
]. A history of MRSA
colonization was defined as isolation of MRSA from any specimens
(i.e., sputum, wound, and urine) within the 6 months before
the onset of SAB. A hospital stay was defined as the le (...truncated)